98 Escort, fuel pump not running..

[12Ounce]

Well, I'm am happy to learn this info. '97 was such a year of big change in the Escort I am surprised the fuel system changed again in '98.

I now suspect your fuel rail does not have the regulator. Did you have a chance to look for it (just for "info")? Do you see a pressure sensor instead?

[12Ounce]

I took a look in "Powertrain Control/Emissions Service Manual" for 1999. This shows three different fuel systems (return, mech returnless, & electronic returnless) used in all gasoline USA Ford cars/trucks for that year. Under the "electronic returnless" system description, it describes a "fuel pump driver module" (FPDM) that varies voltage to the fuel pump module (FPM) based on control info from the PCM.

This must be the system on the '98.

[Selectron]

I've tracked down a couple of photos of the Fuel Pump Driver Module (FPDM) for the Escort. One is a clear photo which applies to a '1998 Ford Escort SE'. I don't know what the policy is here on posting links, so again, I'll send them in a PM.

For the benefit of anybody reading this in the future, it's a small black box which looks like it measures less than 4" high by 3" wide by less than 1" deep. The black box looks plastic, although it may be metallic. It has a bare metal mounting lug at bottom left and another at top right, and it has a large white label attached which, helpfully, says 'FPDM' in large letters, with a Ford part number beneath, and a large barcode beside the lettering. In the clear photo, the part number is F8CF-9D372-AC and in the blurred photo it would appear to be F8CF-9D372-DA. At the bottom of the unit, an electrical connector, around 1" in width protrudes downwards from the enclosure. Presumably, the wiring harness plugs onto this connector. I came across a mention of the FPDM which said that the location in a '98 Escort Sport' is 'inside the vehicle, behind the left hand wheel housing', although that is as yet unconfirmed.

[dllewell]

12 Ounce:
thanks for the info on variable voltage...that seems to fit our assumptions/ theory. It would sure be nice to know over what range that voltage is supposed to vary....

Selectron:
As always, your help is greatly appreciated. I too am beginning to feel more and more like the inital problem was an obstruction in the pump. Curious that it would occur just as i pulled the car into the garage and shut it off (since i first noticed it when tryign to start the next day). Perhaps this is due to the whole static friction vs. moving friction phenomenon?

If i get a chance tonite, i will do at least the first step of back-tracing that you have suggested (measuring voltage from battery + to fuel pump connector + and battery - to FP connector - (though i am currently uncertain how to interpret the results).

I am still hesitant to try to pull the pump out of the tank. Seems like a fairly straight-forward process (though i dont have the correct tool for removing eh locking ring on the pump housing/ fuel tank). It just seems like it could get messy. Generally speaking, i dont like to fool with fuel. Especially when it is doen from inside the car!

i am slowly ragaining confidence in the reliability of my car,
D.

[Selectron]

Interpreting the results is straightforward enough because there are only five possible sets of results, the last two of which are highly unlikely:

• 1. On the positive side, you record 6.6V, with 0V (up to 0.5V is okay) on the negative side
• 2. On the negative side, you record 6.6V, with 0V (up to 0.5V is okay) on the positive side
• 3. On the positive side, you record some voltage, and on the negative side you record some voltage, which when added together total 6.6V
• 4. You record 0V on the positive side, and also 0V on the negative side
• 5. You record some random, perhaps unstable voltage on the positive side, and similar on the negative side, which when added together are nowhere even close to 6.6V - could be way above or way below

Interpret those results as follows:

• 1. This means that the control module is on the positive side of the circuit (if variable-voltage pump), or the high-resistance fault is on the positive side of the circuit (if fixed-voltage pump)
• 2. This means that the control module is on the negative side of the circuit (if variable-voltage pump), or the high-resistance fault is on the negative side of the circuit (if fixed-voltage pump)
• 3. This would suggest that the pump is not variable-voltage but is instead fixed-voltage, and has a high-resistance fault on the positive side of the circuit, plus another high-resistance fault on the negative side of the circuit
• 4. This would suggest that the pump is variable-voltage and fed from a dedicated, isolated power supply, in which case no further checks are possible, beyond locating the control module and ensuring that it is physically well-secured at its mounting lugs, and ensuring that the connector from the wiring harness is firmly seated.
• 5. This would also suggest that the pump is variable-voltage and fed from a dedicated, isolated power supply, so interpret as for #4

In order of probability, when taking the voltage readings, this is what I would expect to see:

• 1. Definitely the most likely
• 2. Less likely, but still possible
• 3. I think this is very unlikely
• 4. Only a very remote chance of this
• 5. Only a very remote chance of this too

[Selectron]

As a footnote to that, I would add this:

The voltage checks won't tell you if you have a variable-voltage pump or a fixed-voltage pump - they will only tell you whether the missing 6.6V is upstream from the pump connector positive terminal, or downstream from the pump connector negative terminal. In order to proceed further, you would then need to determine which type of pump you have, by locating the FPDM - and I'm convinced that it is the variable voltage type.

In the event that it's the fixed voltage type then tracking down the high-resistance connections is straightforward, by taking voltage readings along the path, looking for the point at which the missing 6.6V is being dropped.

In the event that it's the variable voltage type then you can only check that the FPDM is securely mounted and that the wiring harness connector is securely fitted. If you were able to positively identify, and access, the two feed wires to the pump, at the FPDM end, then you could verify that the voltage leaving the FPDM is the same as that which arrives at the pump connector. There isn't really any scope to test beyond that, without access to a spec sheet detailing what the normal voltage range from the FPDM output should be.

[12Ounce]

I've removed a few tanks. Always clumsy/dirty work. You never have enough clearance under the vehicle to work with ... unless its a truck. The tank doesn't weigh much when empty, but there will be road soil on top waiting for you. The lock nut-ring that clamps the pump module to the tank is easily removable with wooden/plastic (avoid sparks) block driven with a hammer. CCW to loosen.

The next time you have a punctured or rusty tank, you may consider driving stateside and buying one from AutoZone. They have to be ordered ahead. Not very expensive.

[12Ounce]

Here's some information, does support the idea that 1998-1999 Escorts had a different fuel system compared to 1997's. (There's an access hole to the fuel pump under the rear seat???). Some elect info, but not much.
.
http://www.autozone.com/servlet/UiBr...3d8013c370.jsp

[dllewell]

So i found the FPDM, located as described (behind the rear driverside wheel well...just under the rear speaker. I am glad that Selectron posted soem pictures or i would have never found it...

I aslo ran some tests:

With the car on i measured voltage as suggested:
Positive Battery terminal to Positive side of fuel pump: 6.4-6.6 V
Negative Battery terminal to Negative side of FP: 0.1 to 0.2 V

Then i tested the FPDM (with car running):

Feed line coming into FPDM: 14.1 V (relativelyconstant regardless of engine speed)

Line exiting FPDM going to FP: 7.9 to 8.1 while idleing, increases to over 9V when i stepped onthe gas (in neutral).

It seems like this is in fact a variable voltage system with the FPDM controlling the voltage going to the pump. Since Selectron found one of these for sale on Ebay and since the bidding ended yesterday and nobody else bid, i would up buying an extra (cost me about 12$ CAD with shipping...well worth it to satisfy my curiosity).

Once i get it, i will make a comparison and post the results. As well, i think i have convinced myself to pull the pump out of the tank and have a look-see. This wont likely happen till January.

cheers till then,
d.

[Selectron]

Thanks for the update, dllewell. The voltage readings are as expected, and confirm two things: firstly that the FPDM is responsible for the 'missing' 6.6V (missing almost certainly by design, but you'll be able to confirm this by substitution when you receive the replacement), and secondly we now know for sure that you have healthy return connections on the negative side of the circuit (from pump connector negative terminal to battery negative terminal). We know that, because resistance = voltage divided by current. The voltage was from 0.1V to 0.2V so we'll call that 0.15V (midpoint) and we know that the current has been measured at 4.1A, so:

resistance = voltage / current
R = 0.15 V / 4.1 A
R = 0.037 Ohms

That's a good ground connection, so no need for further checks on that side of the circuit.

Likewise with the supply feed into the FPDM - at 14.1V it is within 0.1V of full supply voltage, thus indicating good, low-resistance connections on both supply and return sides, so no further checks needed on that.

It was a stroke of luck, finding the FPDM at that price, so it will be money well spent in that it will put your mind at rest if it gives the same voltage readings as the original, which I fully expect that it will. You will then be able to concentrate on what will likely prove to have been the root of the initial problem, which is the contents of the fuel tank.

If it were me, as I said earlier, I'd check out that new filter after four weeks and see what state it's in, compared to the state it was in at four weeks after the tank repair. With a bit of luck, the worst of the contamination may have been filtered out by the old filter, and the new one may prove to be relatively clean once again. I hope so, because otherwise you'll have to put the multimeter away and roll your sleeves up and set about checking out the tank. I'll keep my fingers crossed that it doesn't come to that though and I hope it will continue to run well and reliably.

[dllewell]

I finally tried the new (used) driver module that i Purchased from Ebay:

The voltage to the pump is virtually the same as with the old module as expected.

As far as i can tell, case closed.
Thanks for all you help selectron and 12ounce

D.